drivers: net: cpsw: fix wrong regs access in cpsw_ndo_open

BugLink: http://bugs.launchpad.net/bugs/1625177

The cpsw_ndo_open() could try to access CPSW registers before
calling pm_runtime_get_sync(). This will trigger L3 error:

 WARNING: CPU: 0 PID: 21 at drivers/bus/omap_l3_noc.c:147 l3_interrupt_handler+0x220/0x34c()
 44000000.ocp:L3 Custom Error: MASTER M2 (64-bit) TARGET L4_FAST (Idle): Data Access in Supervisor mode during Functional access

and CPSW will stop functioning.

Hence, fix it by moving pm_runtime_get_sync() before the first access
to CPSW registers in cpsw_ndo_open().
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 3fa88c51)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/ethernet/ti/cpsw.c

@@ -1252,12 +1252,12 @@ static int cpsw_ndo_open(struct net_device *ndev)
 	int i, ret;
 	u32 reg;
 
+	pm_runtime_get_sync(&priv->pdev->dev);
+
 	if (!cpsw_common_res_usage_state(priv))
 		cpsw_intr_disable(priv);
 	netif_carrier_off(ndev);
 
-	pm_runtime_get_sync(&priv->pdev->dev);
-
 	reg = priv->version;
 
 	dev_info(priv->dev, "initializing cpsw version %d.%d (%d)\n",